I have a 2000 gmc sierra extended cab pickup, 1500 series ,2 wheel drive, 4.8 litre engine with automatic transmission.

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Customer: i have a 2000 gmc sierra extended cab pickup, 1500 series ,2 wheel drive, 4.8 litre engine with automatic transmission. I have had a gradual coolant leak. pressure tested system -but im unable to find leak. so i took it to local gmc dealer, and they found whitish ,brown milky coolant in valve covers. told me the heads were cracked, that i needed to replace them. so i removed heads and took to machine shop, had heads pressure tested, they were unable to find cracks or pressure leaks. i did compression test before removing heads ,compression was 150-152 psi in all cylinders. drained oil , found no water in oil. if theres no cracks in cylinder heads and no coolant in oil, how could coolant get into valve covers? truck has never overheated, and water pump is new, please help?
Answered by tim's computer in 3 mins 13 years ago
tim's computer
25+ years of experience

27,680 satisfied customers

Specialities include: Automotive Mechanic, Small Engine Repairs, Auto Body Repairs, Diesel Engine Repairs


the coolant could have got into the engine from the intake gaskets..these are known to have a leaking intake manifold gasket......it is sometimes common to maybe have a little milk look in the oil in cold weather from condensation...


on my 2000 gmc sierra truck ,it has a composite/plastic type of intake manifold. my gm mechanic says no coolant goes into intake manifold. it has coolant piping/tubing in center of motor underneath intake. could it just be caused by blown head gasket, but why wouldnt coolant be in oil.


for some reason i was thinking 5.7,,i got confused with another guy i was talking to


anyways,,yes,it is very possible for it to have been a bad head gasket...i wouldn't think you are loosing much coolant..just a little may not show up in the pan,but accumulate in the valve cover....look around the water pump on this engine,the coolant may be steaming off from the water pump and what you see in the covers is just condensation



Intake Manifold Removal

Important: The intake manifold, throttle body, fuel injection rail, and fuel injectors may be removed as an assembly. If not servicing the individual components, remove the manifold as a complete assembly.
DO NOT reuse the intake manifold-to-cylinder head gaskets.


  1. Remove the Positive Crankcase Ventilation (PCV) hose (1) and valve (2).



  1. Remove the Manifold Absolute Pressure (MAP) sensor (1) (if required).
  2. Remove the engine coolant air bleed clamp and hose from the throttle body.



  1. Remove the accelerator control cable bracket (2) and bolts (1) (if required).



  1. Remove the Evaporative Emission (EVAP) solenoid (3), bolt (2), and isolator (1).



  1. Remove the intake manifold bolts.
  2. Remove the intake manifold with gaskets.



  1. Separate the intake manifold-to-cylinder head gaskets (1) from the manifold.
  2. Discard the intake manifold gaskets.
my 2000 gmc sierra has a 4.8 litre engine. water pump is brand new, it was losing a 1/2 gallon of coolant every 2 weeks or so. after removing valve covers, i only found milky whitish- brown coolant in drivers side valve cover, the one with pcv valve in it. Is it possible for head gasket to only leak coolant into valve cover/rocker arm area without coolant getting into motor oil? or could coolant leak be coming from somewhere else?


it is possible for it to have been blown in the water jacket and cylinder..this would send most the coolant out the exhaust,and some into the oil...the oil in the valve cover is not separated from the pan.....


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tim's computer
27,680 satisfied customers
25+ years of experience
tim's computer
25+ years of experience

27,680 satisfied customers



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